Evaluating the role of Corynebacterium matruchotti MdbA in oral biofilm formation

Oxidative protein folding via disulfide bond formation is a well‐characterized process in Gram‐negative bacteria; however, this pathway has only recently been revealed in the two Gram‐positive actinobacteria Actinomyces oris and Corynebacterium diphtheriae . In these organisms, post‐translocational folding of the majority of proteins exported by the Sec translocon requires a thiol‐disulfide oxidoreductase named MdbA. MdbA is essential for many cellular processes, as genetic disruption of mdbA causes aberrant cell morphology, growth arrest, and attenuation in bacterial virulence. The focus of my work is to characterize a putative MdbA homolog in Corynebacterium matruchotti , a newly found oral actinobacterium proposed to be a key organism in the development of oral biofilms. By molecular techniques, we generated a recombinant MdbA protein of C. matruchotii in E. coli and purified the protein in homogeneity for antibody production. In collaboration with Argonne National Laboratory, we have determined the crystal structure of C. matruchotii MdbA (1.7 Å resolution) that reveals two conserved features present in actinobacterial MdbA proteins: a thioredoxin‐like domain and an extended α‐helical domain. In addition, I found that C. matruchotii forms a monospecies biofilm as determined by the Congo Red assay and that C. matruchotii interacts with Fusobacterium nucleatum , a key pathogen involved in oral biofilm formation. Future experiments will focus on determining if genetic disruption of C. matruchotii mdbA affects cell growth, morphology, biofilm formation, and interaction with F. nucleatum . This study will contribute to our understanding of oxidative protein folding in actinobacteria and allow for research of MdbA inhibitors in actinobacterial pathogens including A. oris , C . diphtheriae , and Mycobacterium tuberculosis .